Solid State Reaction between Tantalum (Ta) and Tantalum Carbide (TaC) Powders during Hiping

At high temperature and pressure, diffusion of carbon occurred between tantalum and tantalum carbide powders. Depending on the initial size of the tantalum grains, various ceramic grades were obtained by sintering Ta and TaC powders. Either an equilibrium composition was reached between the fine metal grains and the tantalum carbide grains, leading to the formation of monolithic but unstoichiometric carbides. On the other hand, under the same experimental conditions, ceramic-metal composites were prepared by using a coarse Ta grains powder. In this last case, tantalum inclusions were dispersed inside the ceramic matrix due to incomplete diffusion process and a carbon concentration gradient was detected at the Ta-TaC interface.